Load support with fluid-pressure type load relief provision



Oct. 8, 1963 J. c. HARTLEY 3,106,431

LOAD SUPPORT WITH FLUID-PRESSURE TYPE LOAD RELIEF PROVISION Eiled Aug.18, 1955 2 Sheets-Sheet 1 IN V EN TOR. James CHQPZZW A7 orngz Get. 8,1963 J. c. HARTLEY 3,106,431

LOAD SUPPORT WITH FLUID-PRESSURE .TYPE LOAD RELIEF PROVISION Filed Aug.18, 1955 2 Sheets-Sheet 2 w T ma ffi it] 1 i IN V EN TOR.

James 6719622 079 BY 3,106,431 LGAD SUPPORT WITH FLUID-PRESSURE TYPELOAD RELIEF PROVISlON liames C. Hartley, Branford, Conn, assignor toUnion Manufacturing Company, New Eritain, (301111., a corporation ofConnecticut Filed Aug. 18, 1955, Ser. No. 529,290 9 Claims. (Cl. 308-)The present invention relates to highly novel and efficientload-supports with fluid pressure-type load-relief provisions, andmethods of fabricating the same.

It is an object of the present invention substantially to eliminate theadverse effects of the weight and friction of a load on the movement ofthe latter or an underlying support, so as to reduce sliding frictionbetween, and hence wear of, the relatively movable parts to a minimumand accordingly greatly reduce the force required to move a heavy loadrelative to its support, as well as eliminate costly bearing provisionsheretofore customarily used for movably supporting heavier loads.

Another object of the present invention is the provision of simplifiedand highly effective means for floating a load, and even a heavy load,on an underlying support for readily adjusting the load relative to thesupport.

A further object of the present invention is the provision of afluid-pressure operated lift mechanism in which fluid under relativelylow pressure is effective to lift most any load, including very heavyloads. In this connection, it is a more specific object to provide apowerful air lift which is operated by air from a supply source underrelatively low compression and has low air consumption.

Another object of the present invention is to provide the aforementionedair lift by providing the mechanism with a passage or passages ofindividual cross-sectional area which is as minute as practicallyfeasible, so that air under low compression forced therethrough willcreate and sustain between the confronting surfaces of the load and itssupport an air film the integral or" the pressure of which is adequateto separate these surfaces, thereby achieving not only relief of a loadby air under low compression in the first place, but also load relief inthis fashion with low-power, small size and low-cost equipment andexceedingly small consumption of work-performing compressed air.

A further object of the present invention is to carry the minutecross-sectional area of the aforementioned air-lift passage or passagesin the mechanism to a sufficient depth to assure that the mechanism willbe of adequate structural strength between the outer or discharge endsof these air passages and their inner ends which are in directcommunication with an internal air supply chamber.

It is another object of the present invention to form the aforementionedmechanism or member of a relatively hard metal, or of a material havingother characteristics which make it difficult or impractical to drillthe aforementioned fine and relatively long passages thereinto, whichmember is nevertheless provided with said air passages withoutencountering the slightest difiiculties in their formation.

In connection with the foregoing object, it is a further object todevise relatively simple methods for providing the fine air passages ina member formed of the aforementioned materials.

It is a further object to devise methods for providing theaforementioned very fine and relatively long passages in relatively hardmaterials, or in materials otherwise excessively resistant to afine-dn'lling operation, without the necessity of drilling through saidmaterials.

Another object is the provision of a member formed of a relatively hardmaterial, or a material which is other- 3 ,i h ,4131 Patented Get. 8,1963 ice 2 wise exceedingly resistant to a fine-drilling operation, andto provide this member, nevertheless, with very fine and relatively longpassages by a drilling operation without encountering any difiicultieswhatever.

A still further object is the provision of a bearing arrangement betweentwo relatively rotatable members, and especially a bearing arrangementsubjected to thrust under considerable loads, which arrangement greatlyreduces the power required to effect their relative rotation,substantially eliminates wear of said members from their relativerotation, and makes lubrication unnecessary.

Other objects and advantages will appear to those skilled in the artfrom the following, considered in conjunction with the accompanyingdrawings.

In the accompanying drawings, in which certain modes of carrying out thepresent invention are shown for illustrative purposes:

FIG. 1 is a fragmentary View, in elevation and partly in section, of amachine tool having a slidable work holder and support therefor,pursuant to one form of the present invention;

FIG. 2 is a fragmentary view, in elevation and partly in section, of amachine tool provided witli a rotary work holder and support therefor,also pursuant to the present invention;

FIG. 3 is a top plan view of a modified form of the support or liftdevice of FIG. 1;

FIG. 4 is a fragmentary section, on an enlarged scale, taken on the line4-t of FIG. 3;

FIG. 5 is a perspective view of a modified form of the support or liftdevice of FIG. 2, prior to the formation of the air passages or ductstherein;

FIG. 6 is a perspective and part-sectional view, on an enlarged scale,of a part of the support member illustrated in FIG. 5;

FIGS. 7 and '8 are enlarged fragmentary sections through the supportmember of FIG. 5 as taken on the lines '77 and 8-8 thereof,respectively, with the member shown in different stages of itsfabrication, however;

FIG. 9 is a fragmentary sectional view of another slidable load carnierand support therefor embodying the present invention in another form;

FIG. 10 is a fragmentary section through still another slidable loadcarrier and support therefor embodying the present invention in afurther modified manner;

FIG. 11 is a fragmentary view as seen in the direction of the arrow 11in FIG. 10;

FIG. 12 is an exploded view of elements cooperating in the formation ofan air duct in the embodiment of FIG. 10;

FIG. 16 is a fragmentary section through a further load support memberembodying the present invention in a further modified form; and

FIG. 14 is a perspective view of a combat tank embodying the presentinvention.

Referring now to FIG. 1 of the drawings in detail, there is shown amachine tool 20 provided with a work holding fixture or jig 2.2 in whicha workpiece 24 is rigidly held or clamped. For illustrative purposesonly, the machine tool 20 is here shown as a conventional multiple drillpress, in which the workpiece 24 is subjected to the action of thedrills 26 provided in the spindles 28. The fixture or carrier 22 ismounted for linear movement on a stationary support or track member 30so that the workpiece 24 may be accurately positioned relative to thedrills 26 for the machining operation.

The workpiece 24- and the fixture 22 may constitute a comparativelyheavy load on the fixed support or table 30 so that a considerableamount of force is required to overcome the effects of the weight andfriction engagement of the loaded fixture on the table 30. However, thisforce is presently derived from compressed air under relatively lowcompression. As here shown, provision is made for a fluid distributingchamber or manifold 32, in this instance an air distributing manifold,which is defined within the table 30. A plurality of air ducts orpassages 34 of very small cross-sectional dimensions extend upwardlyfrom chamber 32 to the upper surface 36 of the support 30 on which theslide or fixture 22 is slidably supported. A conduit or air pipe 33,provided with a shut-off valve 40, extends from the chamber 32 to acompressed air supply which is not illustrated.

When it is desired to move the loaded fixture relative to the stationarysupport, the valve 40 is opened to admit air, under pressure, into thechamber 32. From the chamber, the air fiows through the highlyconstricted passageways defined by the ducts 34 to issue therefrom asair jets which create and sustain an air film between the confrontingsupport and fixture surfaces 36 and 42, respectively. The integral ofpressure of this air film is adequate to lift the fixture 22sufficiently from the support surface 36 actually to float thereon aslong as air under pressure is being supplied to the distribution cham-'ber 32. With the loaded fixture 22 thus floating on the support or table3%, the effects of the weight of the loaded fixture and its friction onthe support are eliminated to all practical intents and purposes, and anoperator may thus move even a very heavy loaded fixture on the support30 with very little effort. After the workpiece is properly positioned,the air valve 40 is .closed and the fixture comes to rest on theunderlying table.

As previously indicated, the air supply'for the manifold 32 need be onlyunder comparatively small compression, for example, the compressed airpressure normally used in industrial plants. Nevertheless, due to theresistance to flow encountered by the air in the air film between theplane machined support and fixture surfaces 36 and 42, and despite somedrop in pressure of the air jets supplying the air film from thepressure of the air supply in the distribution chamber 32, the integralof the pressure of the air film is sufficient to air-float the loadedfixture 22. Consequently, the number of jets applied at spaced points onthe table 30, each to supply an appropriate portion of the air film overthe overall area of the surface 42 of the loaded fixture 22, combine tosustain the air film for the necessary lift of the loaded fixture fromits support '30, air from the film constantly escaping therebetween.

The efficiency of the load lifting performance of the present equipmentundera given pressure increases, within limits, with the reduction inthe cross-sectional area of the individual air ducts 34. Hence, it isimportant from this standpoint, and especially from the standpoint ofobtaining a constant adequate compressed air supply with thelowest-power, smallest size and lowest cost equipment andachieving theload lift with the least consumption of work-performing compressed air,to make the cross-sectional area of these individual ducts as small aspracticable, keeping in mind that the cross-sectional area of theseducts must not be so exceedingly small that the friction of the air jetson the duct walls causes an undue drop of pressure of the former. Theobjective of making these air ducts of the smallest permissiblecrosssectional area prevails even if the load to be lifted from itssupport sufiiciently to air-float thereon is an exceptionally great one,for it is the minute cross-sectional dimension of these ducts which islargely responsible in achieving the above-described economicperformance of the equipment, whereas the magnitude of the load to belifted may conveniently be accommodated by proper selection of thenumber of air ducts and their spacing cross-sectional areas of theseducts are maintained at least to a substantial depth.

Referning now to FIG. 2'in detail, there is shown a machine tool 44provided with afixture or work holding jig 46 which is constituted by aturret mounted for rotary indexing movement on a stud 43 on a fixed base50. The turret 46 has conventional means to secure or clamp theworkpiece 52 in position thereon for the subjection of the workpiece toa machining operation, in this instance to drilling by horizontallyreciprocable multiple drills 54.

The turret 46 is mounted forrotary movement on a stationary table orsupport 56 provided on the base 50. Pursuant to the present invention,the loaded turret 46 may, despite its comparatively heavy weight, bereadily indexed on the table 56 by being air-floated thereon. In thisconnection, the table or air lift means 56 has a circular distributingchamber or manifold 53 provided therein, a conduit or air pipe 60 with ashut-off valve 62 connecting the manifold to an air supply undercomparatively low compression. The relatively long air passages or ducts64, of minute cross-sectional areas extend upwardly from the manifold 58to the upper surface 66 of the table 56.

As in the previously described embodiment, the valve 62 is opened toproduce a plurality of air jets which create and sustain between theupper surface 66 of the table 56 and the bottom surface 63 of the turret46 an air film which will lift the latter above the support '56. Withthe turret floating slightly above the underlying support, the turretmay readily be indexed, without any eal effort or force, the air fromthe air film constantly escaping between the confronting turret andsupport surfaces, as in the previously described. example. After theturret is indexed to properly align the workpiece 52 with the tools 54,the valve s2 is closed and the turret reseats on the support.

As previously indicated, economic performance of the load-lifting orfloating equipment requires very fine air ducts or passages. For manyapplications, it is necessary to provide these ducts or air passages inrigid members formed of hard metal or of a material which is exceedinglyresistant to penetration by very small diameter drills which normallywould be required to drill these fine ducts. In any event and regardlessof theresistance to drilling of the material of the rigid member, thefurther requirement that the minute cross-sectional areas of these airducts be maintained to a considerable depth for adequate structuralstrength of this member makes it all the more difficult to drill theseducts because of the well known and uncontrollable tendency of' veryfine drills to wander offcenter in the process of drilling. Pursuant tothe present invention, provision is made to provide these ducts inmembers made of such hard or otherwise drill-resistant materials,without encountering any difficulties whatso- I ever.

Referring now to FIGS. 3 and 4 in detail, there is illustrated a supporttable or track'70 pursuant to the present invention. As here shown, thesupport 70 is in this instance of rectangular configuration for use, forexample,

as the support table or track in the previously described machine tool20. The table 70 comprises a plate 72 formed of relatively hard steel,cast iron, or other material suitable for its intended vuse,'w-l;iichmaterials are too hard, or the table formedthereof'is too thick, to bedrilled with very small drills which would be required to form thecross-sectional minute and relatively long air duois therein, aspreviously described.

The plate 72 is provided at its upper or load-support surface 74 with acontinuous groove 76 which, as here shown, is of serpentine outline. Thegroove 76 is open at one end thereof, as at 78, at one side of the plate72, and is closed at the otherend thereof, as at 80. A conduit or airpipe 82, which has relatively small wall thickness and may, ifdesired'or feasible, be formed of relatively soft material, such-as,forexample, and not by way of limitation, copper or other easilydrillable material, is press-fitted, or otherwise disposed within thegroove 7 6, with one end of the conduit projecting from the plate 72, asat 84. It will be noted that the diameter of the conduit issubstantially less than the depth of the groove 76, the groove beingfilled above the conduit with a suitable molten metal filling 86, havinga relatively low melting point, which is cast over the conduit to securethe latter in position within the groove. For a suitable fillingmaterial 86, I may use an alloy of zinc, aluminum, copper and magnesium,known as Kirksite, although other suitable metal alloys having lowmelting points may be used.

After the metallic filling hardens, the top surface 74 of the plate 72is planned by a suitable machining operation, such as milling orgrinding. The metallic insert 86 is then drilled at spaced intervals,longitudinally thereof to provide the air ducts or passages 88 whichextend through the upper surface of the conduit 82. Since at least themetallic insert 86 is formed of relatively soft material and the conduit82 has in any event relatively small wall thickness, they may be readilydrilled with very small drills of the required lengths, withoutencountering such resistance as would break the drills even on theirfast advance into the material or cause them to Wander off-center. Theprojecting end 5540f the conduit 82 may be readily connected to theusual industrial compressed air supply, as previously described, toprovide air jets which pass through the ducts 88. The table or airliftsupport 70 may be used to lift a loaded fixture in the same manner asthe previously described air-lift table 30.

Referring now to FIGS. 5 through 8, in detail, there is illustrated amodification of the embodiment of FIG. 3, which is shown in connectionwith an air-lift table of a rotary indexing device, as described inconnection with FIG. 2. As here shown, provision is made for a circularair-lift table or support 90 comprising a circular plate 92 of asuitable metal or other material of the required hardness. The plate 92is formed, in its upper surface 94, with a spiral groove 96. One end ofthe groove 96 is open at the periphery of the plate 92, as at 98, andthe other end is closed as at 199. The plate 92 is, in the presentinstance, formed with integral projections or lugs 102 which extend intothe groove 96, as best illustrated in FIGS. 6 and 7. A conduit or airpipe 104, similar to the previously described conduit 82 in FIGS. 3 and4, is inserted into the groove 96, being forced under the lugs 102 (FIG.7) which serve permanently to retain the conduit in position within thegroove. It will be noted in FIG. 7 that the conduit 104 is, inconsequence of its being forced past the lugs 102, partially deformed orconstricted where it underlies the latter, but the conduit is theresufiiciently open to permit air fiow therethrough. It will be understoodthat the inner end of the conduit is preferably closed and abuts theclosed groove end 1%, while the other open end of the conduit projectsoutwardly of the open groove end 98.

As in the embodiment of FIG. 3, a suitable filler of low melting metalalloy is cast in the groove 96 over the conduit 10.4, as at 106 (FIG.8). After the metal filler 196 is hardened and the upper surface 94suitably planed, fine drills are used to drill through the filler intothe underlying conduit to form the air'ducts 108 at spaced intervalsalong the spiral filler 106. With the projecting end (not illustrated)of the conduit 104 connected to a compressed air supply, the circularair-lift table 91 may be used in the rotary indexing apparatus 44 inlieu of the table 56 thereof, to raise the loaded fixture or turret 46sufliciently for rotary indexing movements thereof.

It will be noted that the conduits 82 and 104 of FIGS. 4 and 8constitute air distribution chambers or manifold-s for their respectiveair ducts and function in the same manner as the previously describedchambers or manifolds 32 and 58.

Referring now to FIG. 9, in detail, there is illustrated anotherembodiment of the present invention, pursuant to which the necessity fordrilling the air passages is obviated. Pursuant to the presentembodiment, a Work holding fixture or jig is mounted for relativemovement on a stationary support or track member 112. A separateair-lift base member or plate 114 is in this instance bolted at 118 tothe bottom surface 116 of the fixture 110. The member 114 is recessed,as at 120, in its upper surface 122 to define an air distributionchamber or manifold 124 between the recessed portion and the overlyingjig surface 116. It will be understood that the chamber 124 is connectedto a compressed air supply in a suitable manner, for example asillustrated in FIG. 2.

In addition to having the recess 120 formed therein, the member 114 isprovided also with bores 126 which extend from the recess 120 throughthe opposite or lower surface 128 of plate 114. Air permeable orporousplugs 130 are press-fitted into or otherwise secured in the bores 126.These plugs may suitably be formed of metal powders, such as for exampleand not by way of limitation, stainless steel powder, copper powder,bronze powder, or other suitable metallic powders. In forming the plugs,the metal powder may be compacted and sintered at pressures below thatwhich will produce air-impermeable compacts. T he compacting pressuremay be adjusted or pre-set to provide a predetermined air permeabilityto obtain desired air-flow characteristics for the plugs.

Compressed air admitted into the chamber 124 will flow through thenumerous air passages formed in the air-permeable plugs 136 to providenumerous extremely fine air jets issuing from the bottom surfaces of theplugs. These air jets will be much finer than air jets produced bydrilled air ducts, even using the extremely small diameter drillsutilized in the embodiments of FIGS. 4 and 8. The numerous fine air jetswill create and sustain between the plate surface 128 and the surface132 of the support table 112 an air film which will lift the loaded jig110 with its air-lift plate 114 from the support 1 12 sufiicieintly topermit their sliding on the latter without any appreciable exertion offorce. After the jig is properly adjusted, the air supply to the chamber124 is interrupted and the loaded jig becomes reseated on the support.

The plugs 130 may be provided in a single plate 114 secured to the jig110, or a plurality of plugged plates 114 may be provided on a singleoverlying plate or jig 110, depending upon the area to be covered. Itwill be readily apparent that the present embodiment may be employedwhere a linear adjustment or movement is to be obtained, as in FIG. 1,or where a rotary movement or adjustment is to be obtained, as in FIG..2.

Referring now to FIGS. 10 through 12, in detail, there is illustratedanother embodiment which also obviates the need to drill the air ducts.The present embodiment is similar to that of FIG. 9 in the provision ofa jig or fixture 134 having an air-lift plate or member 136 secured tothe bottom thereof as by bolts 138, which member is disposed on astationary support or track 140. The member 136 has an air distributionchamber or manifold 140 defined therein, which is connected to acompressed air supply through a shut-off valve, as previously described.

Member 136 i provided with a plurality of bores 1 42 which extend fromthe chamber surface 144 through the lower surface 14-6 :of said member,as best illustrated in FIG. 12. An air-impermeable plug 148 ispress-fitted into each bore "142. Each plug 148 is suitably provided, atits periphery, with a longitudinally extending notch or recess 150 whichdefines, with the adjacent surface of the bore 142, an air duct orpassageway 152 between chambers 140 and surface 146 when the plug isdisposed within the bore.

It will be understood that the cross-sectional areas of the notches 150are quite small so as to define the required cross-sectionally minutei211! passages. In order to prevent these ducts or air passages frombeing blocked due to possible deformation of the notches 15s when theplugs are inserted in the respective bores 142, a wire element 154 of asize substantially to fit the notch in each plug 148 is placed thereinbefore the plug 142 is forced into its associated bore (FIG. 12). Thewire element 154, which may be formed of any suitable materialcharacterized by low elastic limit and relatively high tensile strength,remains within the notch in a plug until the latter is fully inserted inits receiving bore. Thereafter the wire element is retracted from thenotch to leave the latter as a clear air duct 152 (FIGS. and 11). Thefixture 134 provided with the air-lift plate or member 136 will operatein the same manner as the fixture 110 when compressed air is admittedinto the chamber 140 and flows through the air ducts 152.

Under certain conditions, characteristics other than the great strengthof metal, may be required of an airlift table or support. For example,it may be desirable to have an air-lift table which is relatively lightin weight, or highly resistant to abrasion, or non-magnetizable, orresistant to electrical current flow, or a good thermal insulator. Undersuch circumstances, an air-lift table 156 (FIG. 13) may be providedwhich comprises complementary plates 158 and 166 of which at least thethinner plate 166 through which the air ducts 174 are to extend is madeof a material having any one or more of the above-mentioned desiredcharacteristics. Thus, if the air-lift table 156 should have very lowweight and the plate 166 should be highly resistant to abrasion, ornon-magnetic, or a poor thermal conductor, the plate 166 may, forexample, be made from laminated glass fiber cloth into which the airducts 174 of minute crosssectional areas may readily be drilled. Thefiber glass layers of the plate 166 may readily be bonded together, andthe plate 166 bonded to the plate 158 as at 168, with eitherthermoplastic or thermo-setting resins, as is well known to thoseskilled in the art.

While the present invention has, by way of example, been illustrated anddescribed in connection with the shifting of a Work load on a support ofa machine tool, its utility and application is by no means limitedthereto. In this connection, an important application of the presentinvention may reside in its utility for readily and quickly rotating agun turret on a battleship or on a combat tank.

Referring now to FIG. 14, in detail, there is illustrated a tank 176provided with a conventional rotary gun turret 178. The turret 17 8 mayhave a conventional rotary mount rotatable relative to an underlyingstationary support. An air-lift assembly, as in FIGS. 2 and 8, forinstance, may be mounted on the stationary support, or the air-liftassembly may be provided on the bottom of the rotatable mount, :as inFIGS. 9, 10 and 13. In either case, air would be admitted to float therotary mount above its stationary support, as previously described. Thisarrangement will provide a gun turret which is practically noiselesswhen rotated, requires much less power to effect its rotation, and wouldeliminate such wear on the parts as would normally occur in the case ofa mechanical bearing used to effect the rotation of the turret.

The invention may 'be carried out in other specific Ways then thoseherein set forth without departing from the spirit and essentialcharacteristics of the invention, and the present embodiments are,therefore, to be considered in all respects as illustrative and notrestrictive, and all changes coming within the meaning and equivalencyrange of the appended claims are intended to be embraced therein.

What is claimed is:

1. In combination, a support member, a load carrier member disposed innormally surface-to-surface contact on said support member and mountedfor movement thereon, one of said members having defined therein an airchamber and at least one opening which extends from said air chamber tothe contacting surface thereof, an airimpermeable plug filling saidopening and being peripherally notched to define an air duct with thebonding surface of said opening, said air duct being in communicationwith said air chamber and extending to the contacting surface of saidone member, and said one member having provision to connect said airchamber to a compressed air supply whereby to provide a fine air jetissuing from said duct and creating and sustaining between the contactsurfaces of said members an air film to float the load carrier memberabove the support member when compressed air is admitted to saidchamber.

2. The'combination defined in claim *1, further characterized in thatsaid-one member is the load carrier member and the latter has a platesecured to the bottom thereof, the bottom surface of said plateconstituting the contacting surface of the load carrier member, and saidplugged opening is provided in said plate to direct the air jet againstthe contacting surface of the support member.

3. An air lift device comprising a member having an air distributionchamber defined therein between opposite surfaces thereof and adaptedfor connection to a compressed air supply, said member having boresdefined therein which extend from said chamber to one of said surfaces,and plugs of air impermeable material filling said bores, said plugsbeing peripherally notched longitudinally thereof to define air ducts,each of minute crosssectional area, between said chamber and said onesurface.

4. An air lift device as defined in claim 3, further characterized inthat said member is formed by two plates which are secured together anddefine the air chamber therebetween, said bores and said air impermeableplugs being provided in one of said plates.

5. The method of manufacturing an air lift device formed of relativelyhard or drill-resistant material and provided with relatively fine airpassages, said method comprising providing a member formed of relativelyhard material having an air chamber and bores extending from a surfacethereof to said chamber, providing plugs which are peripherally notchedlongitudinally thereof, and tightly inserting the plugs into the bores,with a removable wire element positioned in each notch, and withdrawingthe wire elements from the inserted plugs.

6. An air lift device comprising a pair of rigid members bonded togetherin surface-to-surface contact, one of said members having airdistribution means defined in the contacting surface thereof and adaptedfor connection to a compressed air supply, and the other of said membershaving bores of minute cross-sectional areas defined therein whichcommunicate with said air-distribution means and extend to the oppositesurface of said other member, grgd at least the latter is formed ofbonded layers of glass ers.

7. In combination, a support member, a load carrier member above andmounted for movement with its lower surface on the upper surface of saidsupport member, said support member being formed of relatively hardmetal and having a groove in saidv upper surface, conduit meanspositioned in the bottom of said groove, said conduit means having adiameter less than the depth of said groove, a plurality of lugsprovided on said support member and extending into said groove abovesaid conduit means to retain said conduit means in said groove, and ametallic insert of relatively low melting point filling said grooveabove said conduit means for securing the latter in said groove, saidinsert having a plurality of fine bores extending therethrough and beingin communication with the interior of said conduit means, said conduitmeans being adapted for connection to a compressed air supply, tothereby provide relatively fine air jets issuing from said supportmember for creating and sustaining between the upper surface of saidsupport member and the lower surface of said load carrier member an airfilm to float said carrier member above said support member whencompressed air is admitted to said conduit means.

8. An air lift device comprising a member having a groove in one surfacethereof, a conduit disposed in the bottom of said groove and adapted forconnection to a compressed air supply, the diameter of said conduitbeing less than the depth of said groove, lug means provided in saidgroove above said conduit to retain said conduit in said groove, conduitsecuring insert means filling said groove between said conduit and saidsurface, and a plurality of air duets, each of minute cross-sectionalarea, extending through said insert means to said surface and being incommunication with the interior of said conduit.

9. The method of manufacturing an air lift device formed of relativelyhard drill-resistant material and provided with relatively fine airpassages, said method comprising forming a surface groove in a member ofrelatively hard material, providing retaining lugs on said member whichextend into said groove, locating a conduit in said 16 groove by forcingsaid conduit past said lugs to thereby partially deform said conduit inthe regions of contact with said lugs, positioning said conduit awayfrom said surface, filling said groove between said conduit and saidsurface with a readily drillable material, and drilling with a finedrill through the filling material into said conduit.

References Cited in the file of this patent UNITED STATES PATENTS1,317,987 Niewinski Oct. 7, 1919 2,423,203 Oldham July 1, 1947 2,617,696Honiss Nov. 11, 1952 2,666,981 Sandberg Jan. 26, 1954 2,683,636 WilcoxJuly 13, 1954 FOREIGN PATENTS 528,233 Great Britain Oct. 24, 1940

1. IN COMBINATION, A SUPPORT MEMBER, A LOAD CARRIER MEMBER DISPOSED INNORMALLY SURFACE-TO-SURFACE CONTACT ON SAID SUPPORT MEMBER AND MOUNTEDFOR MOVEMENT THEREON, ONE OF SAID MEMBERS HAVING DEFINED THEREIN AN AIRCHAMBER AND AT LEAST ONE OPENING WHICH EXTENDS FROM SAID AIR CHAMBER TOTHE CONTACTING SURFACE THEREOF, AN AIRIMPERMEABLE PLUG FILLING SAIDOPENING AND BEING PERIPHERALLY NOTCHED TO DEFINE AN AIR DUCT WITH THEBONDING SURFACE OF SAID OPENING, SAID AIR DUCT BEING IN COMMUNICATIONWITH SAID AIR CHAMBER AND EXTENDING TO THE CONTACTING SURFACE OF SAIDONE MEMBER, AND SAID ONE MEMBER HAVING PROVISION TO CONNECT SAID AIRCHAMBER TO A COMPRESSED AIR SUPPLY WHEREBY TO PROVIDE A FINE AIR JETISSUING FROM SAID DUCT AND CREATING AND SUSTAINING BETWEEN THE CONTACTSURFACES OF SAID MEMBERS AN AIR FILM TO FLOAT THE LOAD CARRIER MEMBERABOVE THE SUPPORT MEMBER WHEN COMPRESSED AIR IS ADMITTED TO SAIDCHAMBER.